1. Field of the Invention
The present invention relates to a reticle fabrication system and reticle fabrication method for fabricating a mask (reticle) for a photolithographic process used in fabricating a semiconductor integrated circuit.
2. Description of the Related Art
Photolithographic processes are indispensable as the fabrication process of semiconductor integrated circuits. A photolithographic process typically employs a mask called a reticle on which the desired circuit pattern of a semiconductor integrated circuit is written with a lightproof material such as chromium. In current photolithographic technology, a typical method involves applying photoresist to a semiconductor substrate through which light penetrates such as a quartz glass substrate, and then exposing this substrate with a ¼ to ⅕ reduction to transfer the circuit pattern that has been inscribed on the reticle to the substrate.
A reticle fabrication method of the prior art for fabricating the above-mentioned typical reticle will be described with reference to FIG. 1.
Referring to FIG. 1, CAD data 101, which is a semiconductor integrated circuit design plan, are converted to electron beam (EB) plotting data 103 in first data converter 102. These EB plotting data 103 are supplied as input to EB plotting device 104. EB plotting device 104, based on these EB plotting data 103 that have been supplied as input, plots a figure pattern such as a circuit pattern on preplot reticle 105 to fabricate plotted reticle 106.
Plotted reticle 106 is developed by developer 107 to produce developed reticle 108. Developed reticle 108 is inspected in reticle inspection device 111 to determine whether the figure patterns that have been formed correctly reflect CAD data 101.
CAD data 101 are also converted to inspection data 110 in second data converter 109. Inspection data 110 are supplied as input to reticle inspection device 111, and in reticle inspection device 111, these inspection data 110 are used for confirming the absence of errors in the figure patterns that have been plotted on developed reticle 108. When it has been verified, as a result of this inspection, that the figure patterns have been formed correctly on developed reticle 108, this developed reticle 108 is determined as a quality product and becomes inspected reticle 112.
With the reticle fabrication method described above, if a defect (an error) is detected in developed reticle 108 during the inspection process in reticle inspection device 111, it was extremely difficult to determine whether this error was due to a conversion error in first data converter 102 or second data converter 109 or to a fabrication error in the plotting process or developing process.
Furthermore, with the reticle fabrication method described above, if a conversion error has occurred by first data converter 102 or second data converter 109, the reticle still proceeds through the plotting process and developing process for fabrication, Thus, the reticle will only finally determined to be defective only after detection as an error in the inspection process.
Like reticle inspection device 111, EB plotting device 104 is a device that is expensive, and great importance is placed on improving the effective serviceability ratio. However, operating EB plotting device 104 that plots reticles that are defective, due to EB plotting data 103 that contain data conversion errors, results in a remarkable increase in the fabrication costs. There is the additional problem that reticles that have been fabricated by EB plotting data 103 that contain errors are useless.
To address this problem, Document JP-A-2004-094044 (hereinafter referred to as Document 1) discloses a technique for comparing EB plotting data and inspection data in a data inspection device after data conversion to inspect for the presence or absence of data conversion errors. For data alone that have been determined to be correct as a result of this inspection, the reticles are fabricated through processings by the EB plotting device and developer.
The reticle fabrication method described in the Document 1 will be described with reference to FIG. 2. In FIG. 2, parts that are identical to parts in FIG. 1 are given the same reference numerals, and detailed explanation thereof is here omitted.
Referring to FIG. 2, with the reticle fabrication method described in Document 1, EB plotting data 103 and inspection data 110 are supplied as input to data inspection device 113. Data inspection device 113 compares information relating to figure patterns that is contained in EB plotting data 103 and inspection data 110 that have been supplied as input, to determine whether data conversion has been carried out correctly in first data converter 102 and second data converter 109.
If it is determined in data inspection device 113 that EB plotting data 103 are data in which CAD data 101 have been correctly converted, EB plotting device 104 is permitted to conversely fabricate plotted reticle 106. On the other hand, if it is determined that errors have occurred in the data conversion, the fabrication of plotted reticle 106 in EB plotting device 104 is not performed.
The reticle fabrication method described in Document 1 has the advantage of enabling the detection of data errors before the plotting process in EB plotting device 104 and the inspection process in reticle inspection device 111. However, there is the problems that because the conversion processes in first and second data converters 102 and 109 must still be completed, and these conversion processes are time-consuming, the detection of errors renders the conversion processes themselves useless, resulting in a major loss of useless time.